(kə-my'tə-tĭv, kŏm'yə-tā'tĭv) Of or relating to binary operations for which changing the order of the inputs does not change the result of the operation. For example, addition is commutative, since a + b = b + a for any two numbers a and b, while subtraction is not commutative, since a - b ` a - b unless both a and b are zero. See also associative, distributive.